This application is based on applications Nos. 2000-236724, 2000-238315 and 2000-247439 filed in Japan, the contents of which are hereby incorporated by reference.
1. Field of the Invention
The present invention relates to a solid immersion mirror for use in a microscope which uses light to observe samples, a recording/reproducing apparatus which uses light to record, reproduce and erase information, and the like.
2. Description of the Background Art
An optical microscope which employs a solid immersion lens (abbreviated hereinafter as an xe2x80x9cSILxe2x80x9d) is conventionally known. The SIL is made of a high refractive medium, and light entering the SIL is focused to a predetermined light focusing point on an SIL surface. The use of the SIL achieves the increase in numerical aperture in accordance with the refractive index of the medium. Therefore, bringing an object to be observed into proximity to a near-field region of the light focusing point of the SIL provides a smaller light-focused spot diameter.
It has also been proposed to utilize such characteristics of the SIL to form a minute light spot, thereby achieving recording and reproduction using light. More specifically, a technique has been proposed which utilizes near-field light (not only limited to evanescent light but also including light existing in the near-field region of the light focusing point) near the light focusing point by bringing the light focusing point of the SIL and a recording medium in close proximity to each other, thereby to record and reproduce information on a minute region of the recording medium.
On the other hand, a solid immersion mirror (abbreviated hereinafter as an xe2x80x9cSIMxe2x80x9d) has also been proposed which produces functions similar to those of the SIL by the use of light reflection in a high refractive medium. The SIM which uses light reflection has the advantage of not causing a light-focusing deviation (i.e., chromatic aberration) resulting from wavelengths when light is focused.
Conventional examples of the SIM are disclosed in, for example, Japanese Patent Application Laid-Open No. 11-305132 (1999) and Japanese Patent Application Laid-Open No. 11-238238 (1999). The SIM disclosed in Japanese Patent Application Laid-Open No. 11-305132 has a light source directly mounted to the SIM, and focuses a divergent light beam from the light source. The SIM disclosed in Japanese Patent Application Laid-Open No. 11-238238 focuses collimated light incident sideways on the SIM.
However, when directly mounting the light source to the SIM, it is difficult to adjust the positional relationship between the SIM and the light source, and therefore a high mounting accuracy is required. Further, when the SIM is mounted to a so-called floating slider similar to that of a hard disc for recording and reproduction, there arises another problem in increased weight of the floating slider.
The SIM disclosed in Japanese Patent Application Laid-Open No. 11-305132 has a lower surface which is flat and reflects light therefrom. Since the SIM is used in close proximity to an object, the SIM having the lower surface which is flat and serves as a reflecting surface has a high possibility that the lower surface contacts the object, and is in danger of damages to the reflecting surface.
As in the SIM disclosed in Japanese Patent Application Laid-Open No. 11-238238, on the other hand, the collimated light incident sideways on the SIM cannot impinge on the light focusing point uniformly (i.e., at uniform intensity from various directions) to result in an expanded or elliptical spot formed at the light focusing point. Uniform impingement of the light on the light focusing point requires previous control of an intensity distribution of the incident collimated light. It is, however, practically difficult to provide such an optical means.
The present invention is intended for a solid immersion mirror device made principally of a light-permeable medium having a refractive index of greater than 1.According to a first aspect of the present invention, the solid immersion mirror device comprises: a first reflecting surface which is part of a curved surface produced by rotating a parabola about a symmetry axis thereof; and a second reflecting surface which is part of a plane perpendicular to a line segment connecting the focus of the parabola and the vertex of the parabola, wherein collimated light entering the medium from the second reflecting surface side along the symmetry axis is reflected sequentially from the first and second reflecting surfaces while propagating in the medium, and is then focused to a light focusing point on a boundary of the medium.
The first reflecting surface is part of the curved surface produced by rotating the parabola. This facilitates the design of the shapes of the first and second reflecting surfaces, and achieves the formation of a proper light spot at the light focusing point.
According to a second aspect of the present invention, the solid immersion mirror device comprises: a first reflecting surface which is part of a curved surface produced by rotating part of a parabola lying on the opposite side of a rotational axis from the vertex of the parabola about the rotational axis, the rotational axis being parallel to the symmetry axis of the parabola and intersecting the parabola at a position spaced apart from the vertex of the parabola; and a second reflecting surface which part of a conical surface produced by rotating part of a line lying on the opposite side of the rotational axis from the vertex, the line being perpendicular to a line segment connecting the focus of the parabola and a point of intersection of the parabola and the rotational axis within a plane including the parabola, wherein collimated light entering the medium from the second reflecting surface side along the rotational axis is reflected sequentially from the first and second reflecting surfaces while propagating in the medium, and is then focused to a light focusing point on a boundary of the medium.
The first reflecting surface is part of the curved surface produced by rotating the parabola. This also facilitates the design of the shapes of the first and second reflecting surfaces, and achieves the formation of a proper light spot at the light focusing point.
According to a third aspect of the present invention, the solid immersion mirror device comprises: a first reflecting surface of a substantially annular shape and provided in a lower portion of the medium; and second reflecting surface provided in an upper portion of the medium, wherein light entering the medium in a predetermined direction from the upper portion to the lower portion is reflected sequentially from the first and second reflecting surfaces while propagating in the medium, and is then focused to a light focusing point on a boundary of the medium, and wherein part of light reflected from the first reflecting surface is reflected from near a point of intersection of the second reflecting surface and a line passing through the light focusing point and parallel to the predetermined direction.
This enables light with a small incident angle to be incident on the light focusing point, thereby forming a proper light spot at the light focusing point.
According to a fourth aspect of the present invention, the solid immersion mirror device comprises: a first reflecting surface provided in a lower portion of the medium; and a second reflecting surface provided in an upper portion of the medium, wherein at least part of light entering the medium in a predetermined direction from the upper portion to the lower portion passes through the second reflecting surface, is thereafter reflected sequentially from the first and second reflecting surfaces while propagating in the medium, and is then focused to a light focusing point on a boundary of the medium.
This enables light to pass through the second reflecting surface to enter the medium, thereby utilizing the light efficiently.
According to a fifth aspect of the present invention, the solid immersion mirror device comprises: an upper surface formed in an upper portion of the medium; and a side reflecting surface of a substantially tubular shape extending from the upper portion to a lower portion of the medium, wherein light entering the medium by way of the upper surface in a direction from the upper portion to the lower portion is reflected once from the side reflecting surface while propagating in the medium, and is then focused to a light focusing point on a boundary of the lower portion.
This prevents damages to the reflecting surface of the solid immersion mirror device.
According to a sixth aspect of the present invention, the solid immersion mirror device comprises: a light incident point positioned on a boundary of an upper portion of the medium; and a side reflecting surface of a substantially tubular shape extending from the upper portion to a lower portion of the medium, wherein divergent light entering the medium from the light incident point is reflected once from the side reflecting surface while propagating in the medium, and is then focused to a light focusing point on a boundary of the lower portion.
This also prevents damages to the reflecting surface of the solid immersion mirror device.
According to a seventh aspect of the present invention, the solid immersion mirror device comprises: a light incident point positioned on a boundary of an upper portion of the medium; a first reflecting surface positioned in a lower portion of the medium and having a downwardly protruding convex shape; and a second reflecting surface positioned in the upper portion, wherein divergent light entering the medium from the light incident point is reflected sequentially from the first and second reflecting surfaces while propagating in the medium, and is then focused to a light focusing point on a boundary of the lower portion.
This also prevents damages to the reflecting surfaces of the solid immersion mirror device.
According to an eighth aspect of the present invention, the solid immersion mirror device comprises: a light incident point positioned on a boundary of the medium; a first reflecting surface; and a second reflecting surface, wherein divergent light entering the medium from the light incident point is reflected from the first reflecting surface to be converted into collimated light while propagating in the medium, and the collimated light is reflected from the second reflecting surface and is then focused to a light focusing point on a boundary of the medium.
This increases the flexibility in determining the positional relationship between the light incident point and the light focusing point.
The present invention is also intended for a reproducing apparatus.
It is therefore a primary object of the present invention to provide an SIM of a more preferable new form.
It is a specific object of the present invention to provide a solid immersion mirror (SIM) capable of forming a proper light-focused spot when light from a light source enters the SIM, and a reproducing apparatus which uses such an SIM.
It is another specific object of the present invention to provide a solid immersion mirror capable of forming a proper light-focused spot without reflecting light from a lower surface thereof, and a reproducing apparatus which uses such an SIM.